US Car Tool A518 Cross member

I asked
Not arguing, but seems hard to believe they 46RH controller wouldn't work on a 42RH. The plug is the same, they function the same, one is just more HD. But I'm no expert, so maybe I am missing something.
I asked PATC if I could buy the 46RH controller kit, and use it on a 42RH. They told me it would not work on a 42RH. I did not want to spend that kind of cash to find out it doesnt work.